document_title: Ionic compound

question_text: how lattice energy control the solubility of ionic compound

root

text: Ionic compound

text: History of discovery[edit]

text: The word ion is the Greek ἰόν, ion, "going", the present participle of ἰέναι, ienai, "to go". This term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium.[1][2]

tag: p

text: In 1913 the crystal structure of sodium chloride was determined by William Henry Bragg and William Lawrence Bragg.[3][4][5] This revealed that there were six equidistant nearest-neighbours for each atom, demonstrating that the constituents were not arranged in molecules or finite aggregates, but instead as a network with long-range crystalline order.[5] Many other inorganic compounds were also found to have similar structural features.[5] These compounds were soon described as being constituted of ions rather than neutral atoms, but proof of this hypothesis was not found until the mid-1920s, when X-ray reflection experiments (which detect the density of electrons), were performed.[5][6]

text: Principal contributors to the development of a theoretical treatment of ionic crystal structures were Max Born, Fritz Haber, Alfred Landé, Erwin Madelung, Paul Peter Ewald, and Kazimierz Fajans.[7] Born predicted crystal energies based on the assumption of ionic constituents, which showed good correspondence to thermochemical measurements, further supporting the assumption.[5]

text: Formation[edit]

text: Ionic compounds can be produced from their constituent ions by evaporation, precipitation, or freezing. Reactive metals such as the alkali metals can react directly with the highly electronegative halogen gases to form an ionic product.[8] They can also be synthesized as the product of a high temperature reaction between solids.[9]

text: If the ionic compound is soluble in a solvent, it can be obtained as a solid compound by evaporating the solvent from this electrolyte solution.[10] As the solvent is evaporated, the ions do not go into the vapour, but stay in the remaining solution, and when they become sufficiently concentrated, nucleation occurs, and they crystallize into an ionic compound. This process occurs widely in nature, and is the means of formation of the evaporite minerals.[11] Another method of recovering the compound from solution involves saturating a solution at high temperature and then reducing the solubility by reducing the temperature until the solution is supersaturated and the solid compound nucleates.[10]

text: Insoluble ionic compounds can be precipitated by mixing two solutions, one with the cation and one with the anion in it. Because all solutions are electrically neutral, the two solutions mixed must also contain counterions of the opposite charges. To ensure that these do not contaminate the precipitated ionic compound, it is important to ensure they do not also precipitate.[12] If the two solutions have hydrogen ions and hydroxide ions as the counterions, they will react with one another in what is called an acid–base reaction or a neutralization reaction to form water.[13] Alternately the counterions can be chosen to ensure that even when combined into a single solution they will remain soluble as spectator ions.[12]

text: If the solvent is water in either the evaporation or precipitation method of formation, in many cases the ionic crystal formed also includes water of crystallization, so the product is known as a hydrate, and can have very different chemical properties.[14]

text: Molten salts will solidify on cooling to below their freezing point.[15] This is sometimes used for the solid-state synthesis of complex ionic compounds from solid reactants, which are first melted together.[16] In other cases, the solid reactants do not need to be melted, but instead can react through a solid-state reaction route. In this method the reactants are repeatedly finely ground into a paste, and then heated to a temperature where the ions in neighbouring reactants can diffuse together during the time the reactant mixture remains in the oven.[9] Other synthetic routes use a solid precursor with the correct stoichiometric ratio of non-volatile ions, which is heated to drive off other species.[9]

text: In some reactions between highly reactive metals (usually from Group 1 or Group 2) and highly electronegative halogen gases, or water, the atoms can be ionized by electron transfer,[17] a process thermodynamically understood using the Born–Haber cycle.[18]

text: Bonding[edit]

text: Ions in ionic compounds are primarily held together by the electrostatic forces between the charge distribution of these bodies, and in particular the ionic bond resulting from the long-ranged Coulomb attraction between the net negative charge of the anions and net positive charge of the cations.[19] There is also a small additional attractive force from van der Waals interactions which contributes only around 1–2% of the cohesive energy for small ions.[20] When a pair of ions comes close enough for their outer electron shells (most simple ions have closed shells) to overlap, a short-ranged repulsive force occurs,[21] due to the Pauli exclusion principle.[22] The balance between these forces leads to a potential energy well with a minimum energy when the nuclei are separated by a specific equilibrium distance.[21]

text: If the electronic structure of the two interacting bodies is affected by the presence of one another, covalent interactions (non-ionic) also contribute to the overall energy of the compound formed.[23] Ionic compounds are rarely purely ionic, i.e. held together only by electrostatic forces. The bonds between even the most electronegative/electropositive pairs such as those in caesium fluoride exhibit a small degree of covalency.[24][25] Conversely, covalent bonds between unlike atoms often exhibit some charge separation and can be considered to have a partial ionic character.[23] The circumstances under which a compound will have ionic or covalent character can typically be understood using Fajans' rules, which use only charges and the sizes of each ion. According to these rules, compounds with the most ionic character will have large positive ions with a low charge, bonded to a small negative ion with a high charge.[26] More generally HSAB theory can be applied, whereby the compounds with the most ionic character are those consisting of hard acids and hard bases: small, highly charged ions with a high difference in electronegativities between the anion and cation.[27][28] This difference in electronegativities means that the charge separation, and resulting dipole moment, is maintained even when the ions are in contact (the excess electrons on the anions are not transferred or polarized to neutralize the cations).[29]

text: Structure[edit]

text: Ions typically pack into extremely regular crystalline structures, in an arrangement that minimizes the lattice energy (maximizing attractions and minimizing repulsions). The lattice energy is the summation of the interaction of all sites with all other sites. For unpolarizable spherical ions only the charges and distances are required to determine the electrostatic interaction energy. For any particular ideal crystal structure, all distances are geometrically related to the smallest internuclear distance. So for each possible crystal structure, the total electrostatic energy can be related to the electrostatic energy of unit charges at the nearest neighbour distance by a multiplicative constant called the Madelung constant[21] that can be efficiently computed using an Ewald sum.[30] When a reasonable form is assumed for the additional repulsive energy, the total lattice energy can be modelled using the Born–Landé equation,[31] the Born–Mayer equation, or in the absence of structural information, the Kapustinskii equation.[32]

text: Using an even simpler approximation of the ions as impenetrable hard spheres, the arrangement of anions in these systems are often related to close-packed arrangements of spheres, with the cations occupying tetrahedral or octahedral interstices.[33][34] Depending on the stoichiometry of the ionic compound, and the coordination (principally determined by the radius ratio) of cations and anions, a variety of structures are commonly observed,[35] and theoretically rationalized by Pauling's rules.[36]

text:
Common ionic compound structures with close-packed anions[35]

Stoichiometry
Cation:anion coordination
Interstitial sites
Cubic close packing of anions
Hexagonal close packing of anions

occupancy
critical radius ratio
name
Madelung constant
name
Madelung constant

MX
6:6
all octahedral
0.4142[33]
sodium chloride
1.747565[37]
nickeline
<1.73[a][38]

4:4
alternate tetrahedral
0.2247[39]
zinc blende
1.6381[37]
wurtzite
1.641[5]

MX2
8:4
all tetrahedral
0.2247
fluorite
5.03878[40]

6:3
half octahedral (alternate layers fully occupied)
0.4142
cadmium chloride
5.61[41]
cadmium iodide
4.71[40]

MX3
6:2
one-third octahedral
0.4142
rhodium(III) bromide[b][42][43]
6.67[44][c]
bismuth iodide
8.26[44][d]

M2X3
6:4
two-thirds octahedral
0.4142

corundum
25.0312[40]

ABO3

two-thirds octahedral
0.4142

ilmenite
depends on charges and structure [e]

AB2O4

one-eighth tetrahedral and one-half octahedral
rA/rO = 0.2247, rB/rO = 0.4142[f]
spinel, inverse spinel
depends on cation site distributions[47][48][49]
olivine
depends on cation site distributions[50]

tag: table

text: In some cases the anions take on a simple cubic packing, and the resulting common structures observed are:

text:
Common ionic compound structures with simple cubic packed anions[43]

Stoichiometry
Cation:anion coordination
Interstitial sites occupied
Example structure

name
critical radius ratio
Madelung constant

MX
8:8
entirely filled
cesium chloride
0.7321[51]
1.762675[37]

MX2
8:4
half filled
calcium fluoride

M2X
4:8
half filled
lithium oxide

text: Some ionic liquids, particularly with mixtures of anions or cations, can be cooled rapidly enough that there is not enough time for crystal nucleation to occur, so an ionic glass is formed (with no long-range order).[52]

text: Defects[edit]

text: Within an ionic crystal, there will usually be some point defects, but to maintain electroneutrality, these defects come in pairs.[53] Frenkel defects consist of a cation vacancy paired with a cation interstitial and can be generated anywhere in the bulk of the crystal,[53] occurring most commonly in compounds with a low coordination number and cations that are much smaller than the anions.[54] Schottky defects consist of one vacancy of each type, and are generated at the surfaces of a crystal,[53] occurring most commonly in compounds with a high coordination number and when the anions and cations are of similar size.[54] If the cations have multiple possible oxidation states, then it is possible for cation vacancies to compensate for electron deficiencies on cation sites with higher oxidation numbers, resulting in a non-stoichiometric compound.[53] Another non-stoichiometric possibility is the formation of an F-center, a free electron occupying an anion vacancy.[55] When the compound has three or more ionic components, even more defect types are possible.[53] All of these point defects can be generated via thermal vibrations and have an equilibrium concentration. Because they are energetically costly, but entropically beneficial, they occur in greater concentration at higher temperatures. Once generated, these pairs of defects can diffuse mostly independently of one another, by hopping between lattice sites. This defect mobility is the source of most transport phenomena within an ionic crystal, including diffusion and solid state ionic conductivity.[53] When vacancies collide with interstitials (Frenkel), they can recombine and annihilate one another. Similarly vacancies are removed when they reach the surface of the crystal (Schottky). Defects in the crystal structure generally expand the lattice parameters, reducing the overall density of the crystal.[53] Defects also result in ions in distinctly different local environments, which causes them to experience a different crystal-field symmetry, especially in the case of different cations exchanging lattice sites.[53] This results in a different splitting of d-electron orbitals, so that the optical absorption (and hence colour) can change with defect concentration.[53]

text: Properties[edit]

text: Acidity/basicity[edit]

text: Ionic compounds containing hydrogen ions (H+) are classified as acids, and those containing electropositive cations[56] and basic anions ions hydroxide (OH−) or oxide (O2−) are classified as bases. Other ionic compounds are known as salts and can be formed by acid–base reactions.[57] If the compound is the result of a reaction between a strong acid and a weak base, the result is an acidic salt. If it is the result of a reaction between a strong base and a weak acid, the result is a basic salt. If it is the result of a reaction between a strong acid and a strong base, the result is a neutral salt. Weak acids reacted with weak bases can produce ionic compounds with both the conjugate base ion and conjugate acid ion, such as ammonium acetate.

text: Some ions are classed as amphoteric, being able to react with either an acid or a base.[58] This is also true of some compounds with ionic character, typically oxides or hydroxides of less-electropositive metals (so the compound also has significant covalent character), such as zinc oxide, aluminium hydroxide, aluminium oxide and lead(II) oxide.[59]

text: Melting and boiling points[edit]

text: Electrostatic forces between particles are strongest when the charges are high, and the distance between the nuclei of the ions is small. In such cases, the compounds generally have very high melting and boiling points and a low vapour pressure.[60] Trends in melting points can be even better explained when the structure and ionic size ratio is taken into account.[61] Above their melting point ionic solids melt and become molten salts (although some ionic compounds such as aluminium chloride and iron(III) chloride show molecule-like structures in the liquid phase).[62] Inorganic compounds with simple ions typically have small ions, and thus have high melting points, so are solids at room temperature. Some substances with larger ions, however, have a melting point below or near room temperature (often defined as up to 100 °C), and are termed ionic liquids.[63] Ions in ionic liquids often have uneven charge distributions, or bulky substituents like hydrocarbon chains, which also play a role in determining the strength of the interactions and propensity to melt.[64]

text: Even when the local structure and bonding of an ionic solid is disrupted sufficiently to melt it, there are still strong long-range electrostatic forces of attraction holding the liquid together and preventing ions boiling to form a gas phase.[65] This means that even room temperature ionic liquids have low vapour pressures, and require substantially higher temperatures to boil.[65] Boiling points exhibit similar trends to melting points in terms of the size of ions and strength of other interactions.[65] When vapourized, the ions are still not freed of one another. For example, in the vapour phase sodium chloride exists as diatomic "molecules".[66]

text: Brittleness[edit]

text: Most ionic compounds are very brittle. Once they reach the limit of their strength, they cannot deform malleably, because the strict alignment of positive and negative ions must be maintained. Instead the material undergoes fracture via cleavage.[67] As the temperature is elevated (usually close to the melting point) a ductile–brittle transition occurs, and plastic flow becomes possible by the motion of dislocations.[67][68]

text: Compressibility[edit]

text: The compressibility of an ionic compound is strongly determined by its structure, and in particular the coordination number. For example, halides with the caesium chloride structure (coordination number 8) are less compressible than those with the sodium chloride structure (coordination number 6), and less again than those with a coordination number of 4.[69]

text: Solubility[edit]

text: When ionic compounds dissolve, the individual ions dissociate and are solvated by the solvent and dispersed throughout the resulting solution.[70] Because the ions are released into solution when dissolved, and can conduct charge, soluble ionic compounds are the most common class of strong electrolytes, and their solutions have a high electrical conductivity.[71]

text: The solubility is highest in polar solvents (such as water) or ionic liquids, but tends to be low in nonpolar solvents (such as petrol/gasoline).[72] This is principally because the resulting ion–dipole interactions are significantly stronger than ion-induced dipole interactions, so the heat of solution is higher. When the oppositely charged ions in the solid ionic lattice are surrounded by the opposite pole of a polar molecule, the solid ions are pulled out of the lattice and into the liquid. If the solvation energy exceeds the lattice energy, the negative net enthalpy change of solution provides a thermodynamic drive to remove ions from their positions in the crystal and dissolve in the liquid. In addition, the entropy change of solution is usually positive for most solid solutes like ionic compounds, which means that their solubility increases when the temperature increases.[73] There are some unusual ionic compounds such as cerium(III) sulfate, where this entropy change is negative, due to extra order induced in the water upon solution, and the solubility decreases with temperature.[73]

text: Electrical conductivity[edit]

text: Although ionic compounds contain charged atoms or clusters, these materials do not typically conduct electricity to any significant extent when the substance is solid. In order to conduct, the charged particles must be mobile rather than stationary in a crystal lattice. This is achieved to some degree at high temperatures when the defect concentration increases the ionic mobility and solid state ionic conductivity is observed. When the ionic compounds are dissolved in a liquid or are melted into a liquid, they can conduct electricity because the ions become completely mobile.[74] This conductivity gain upon dissolving or melting is sometimes used as a defining characteristic of ionic compounds.[75]

text: In some unusual ionic compounds: fast ion conductors, and ionic glasses,[52] one or more of the ionic components has a significant mobility, allowing conductivity even while the material as a whole remains solid.[76] This is often highly temperature dependant, and may be the result of either a phase change or a high defect concentration.[76] These materials are used in all solid-state supercapacitors, batteries, and fuel cells, and in various kinds of chemical sensors.[77][78]

text: Colour[edit]

text: The colour of an ionic compound is often different to the colour of an aqueous solution containing the constituent ions,[79] or the hydrated form of the same compound.[14]

text: The anions in compounds with bonds with the most ionic character tend to be colourless (with an absorption band in the ultraviolet part of the spectrum).[80] In compounds with less ionic character, their colour deepens through yellow, orange, red and black (as the absorption band shifts to longer wavelengths into the visible spectrum).[80]

text: The absorption band of simple cations shift toward shorter wavelength when they are involved in more covalent interactions.[80] This occurs during hydration of metal ions, so colourless anhydrous ionic compounds with an anion absorbing in the infrared can become colourful in solution.[80]

text: Uses[edit]

text: Ionic compounds have long had a wide variety of uses and applications. Many minerals are ionic.[81] Humans have processed common salt (sodium chloride) for over 8000 years, using it first as a food seasoning and preservative, and now also in manufacturing, agriculture, water conditioning, for de-icing roads, and many other uses.[82] Many ionic compounds are so widely used in society that they go by common names unrelated to their chemical identity. Examples of this include borax, calomel, milk of magnesia, muriatic acid, oil of vitriol, saltpeter, and slaked lime.[83]

text: Soluble ionic compounds like salt can easily be dissolved to provide electrolyte solutions. This is a simple way to control the concentration and ionic strength. The concentration of solutes affects many colligative properties, including increasing the osmotic pressure, and causing freezing-point depression and boiling-point elevation.[84] Because the solutes are charged ions they also increase the electrical conductivity of the solution.[85] The increased ionic strength reduces the thickness of the electrical double layer around colloidal particles, and therefore the stability of emulsions and suspensions.[86]

text: The chemical identity of the ions added is also important in many uses. For example, fluoride containing compounds are dissolved to supply fluoride ions for water fluoridation.[87]

text: Solid ionic compounds have long been used as paint pigments, and are resistant to organic solvents, but are sensitive to acidity or basicity.[88] Since 1801 pyrotechnicians have described and widely used metal-containing ionic compounds as sources of colour in fireworks.[89] Under intense heat, the electrons in the metal ions or small molecules can be excited.[90] These electrons later return to lower energy states, and release light with a colour spectrum characteristic of the species present.[91][92]

text: In chemistry, ionic compounds are often used as precursors for high-temperature solid-state synthesis.[93]

text: Many metals are geologically most abundant as ionic compounds within ores.[94] To obtain the elemental materials, these ores are processed by smelting or electrolysis, in which redox reactions occur (often with a reducing agent such as carbon) such that the metal ions gain electrons to become neutral atoms.[95][96]

text: Nomenclature[edit]

text:
According to the nomenclature recommended by IUPAC, ionic compounds are named according to their composition, not their structure.[97] In the most simple case of a binary ionic compound with no possible ambiguity about the charges and thus the stoichiometry, the common name is written using two words.[98] The name of the cation (the unmodified element name for monatomic cations) comes first, followed by the name of the anion.[99][100] For example, MgCl2 is named magnesium chloride, and Na2SO4 is named sodium sulfate (SO2−
4, sulfate, is an example of a polyatomic ion). To obtain the empirical formula from these names, the stoichiometry can be deduced from the charges on the ions, and the requirement of overall charge neutrality.

text: If there are multiple different cations and/or anions, multiplicative prefixes (di-, tri-, tetra-, ...) are often required to indicate the relative compositions,[101] and cations then anions are listed in alphabetical order.[102] For example, KMgCl3 is named magnesium potassium trichloride to distinguish it from K2MgCl4, magnesium dipotassium tetrachloride[103] (note that in both the empirical formula and the written name, the cations appear in alphabetical order, but the order varies between them because the symbol for potassium is K).[104] When one of the ions already has a multiplicative prefix within its name, the alternate multiplicative prefixes (bis-, tris-, tetrakis-, ...) are used.[105] For example, Ba(BrF4)2 is named barium bis(tetrafluoridobromate).[106]

text:
Compounds containing one or more elements which can exist in a variety of charge/oxidation states will have a stoichiometry that depends on which oxidation states are present, to ensure overall neutrality. This can be indicated in the name by specifying either the oxidation state of the elements present, or the charge on the ions.[106] Because of the risk of ambiguity in allocating oxidation states, IUPAC prefers direct indication of the ionic charge numbers.[106] These are written as an arabic integer followed by the sign (... , 2−, 1−, 1+, 2+, ...) in parentheses directly after the name of the cation (without a space separating them).[106] For example, FeSO4 is named iron(2+) sulfate (with the 2+ charge on the Fe2+ ions balancing the 2− charge on the sulfate ion), whereas Fe2(SO4)3 is named iron(3+) sulfate (because the two iron ions in each formula unit each have a charge of 3+, to balance the 2− on each of the three sulfate ions).[106] Stock nomenclature, still in common use, writes the oxidation number in Roman numerals (... , −II, −I, 0, I, II, ...). So the examples given above would be named iron(II) sulfate and iron(III) sulfate respectively.[107] For simple ions the ionic charge and the oxidation number are identical, but for polyatomic ions they often differ. For example, the uranyl(2+) ion, UO2+
2, has uranium in an oxidation state of +6, so would be called a dioxouranium(VI) ion in Stock nomenclature.[108] An even older naming system for metal cations, also still widely used, appended the suffixes -ous and -ic to the Latin root of the name, to give special names for the low and high oxidation states.[109] For example, this scheme uses "ferrous" and "ferric", for iron(II) and iron(III) respectively,[109] so the examples given above were classically named ferrous sulfate and ferric sulfate.


document_title: The Walking Dead (season 1)

question_text: the walking dead season 1 episode 2 release date

text: The Walking Dead (season 1)

text: Production[edit]

text: Conception[edit]

text: Robert Kirkman, who created the comic book series in 2003,[6] says he had considered the idea of a Walking Dead television series, but never actively pursued it. "I certainly wanted it to happen, just because I knew it would be good for the book... I'm certainly not against adaptations, like some creators."[7] When Frank Darabont became interested in adapting the comic books for television, Kirkman said it was "extremely flattering" and went on to say that, "He definitely cares about the original source material, and you can tell that in the way he's adapting it. It's an extreme validation of the work... Never in a million years could I have thought that if Walking Dead were to ever be adapted that everything would be going this well. I think that that's all because of Frank."[7]

text: Darabont himself had been a fan of the zombie genre since seeing George A. Romero's 1968 film Night of the Living Dead when he was fourteen years old.[8] ""Night of the Living Dead" had this weird vibe that was almost - it was like pornography... It had this marvelously attractive, disreputable draw... I loved it immediately."[9] Darabont recalls walking into a comic book store in Burbank, California and seeing The Walking Dead on the shelf in 2005. "Being that I've always had "the love of zombies genre," I of course grabbed it, took it home and read it, and immediately started pursuing the rights to it. I thought it would make a great TV show... I loved the idea of an extended, ongoing, serialized dramatic presentation set in the zombie apocalypse."[9] He described the process of developing the series and getting it set up at a network as "four years of frustration," and credits executive producer Gale Anne Hurd with finally getting the series on AMC. "I can't remember what the hell prompted her to read it [the script], but she said, "Wow, I really love this pilot you wrote. What are you doing with it?" I said I'd been trying to set it up forever... She said "I think AMC might be the place to take this." She did, and then bam! They were immediately interested. I had to credit Gale, her insight into marrying the material and the buyer."[9]

text: Writing[edit]

text: Darabont's original pilot script was split in half and embellished, making the first two episodes instead of one, "...just to slow the narrative down and dig into the characters more deeply, so it's not just plot-driven, event-driven stuff. You really want to drag these characters into the equation."[9] To write the remaining episodes of the season, Darabont recruited Charles H. Eglee, Adam Fierro and Glen Mazzara, all of whom he had worked with while directing an episode of The Shield. Jack LoGiudice also joined the writing team, along with Robert Kirkman, also an executive producer. "I have the best of both worlds," says Kirkman. "It was a lot of fun writing Episode 104, and I'm hoping if it continues into Season 2, I'll be able to write more episodes."[7]

text: Filming[edit]

text: Principal photography for the pilot episode, "Days Gone Bye", began on May 15, 2010[10] with the subsequent five episodes beginning filming a few weeks later on June 2.[11] The first season was filmed in and around Atlanta, Georgia where the episodes were primarily set.[12]

text: Cast[edit]

text: Main cast[edit]

text: The first season features seven actors receiving opening credits billing:

text:
Andrew Lincoln as Rick Grimes, the series' protagonist and former sheriff's deputy from King County, Georgia, who awakens from a coma into the apocalypse. After becoming aware of the apocalypse, Rick sets out to find his wife, Lori, and son, Carl.
Jon Bernthal as Shane Walsh, Rick's best friend since high school and former colleague, who helped Rick's family escape the apocalypse and is the leader of the Atlanta camp. Believing Rick to be dead, he also started a relationship with Lori, leading to complications when Rick unexpectedly returns alive and well.
Sarah Wayne Callies as Lori Grimes, Rick's wife and mother of Carl.[13] Lori is an emotionally fragile yet independent woman, who started a relationship with Shane out of her grief for losing Rick, leaving her off-guard and very conflicted when Rick returns.[14]
Laurie Holden as Andrea, a former successful civil rights attorney and sister of Amy. Andrea has a slight temper, but has a compassionate side and is very protective of her sister; both of them share a close bond with Dale.
Jeffrey DeMunn as Dale Horvath, an elderly survivor, who owns the RV around which the survivors have formed a camp. Dale is a wise man of morals, who isn't afraid to voice his opinion and is very protective of everyone's well-being, physically and emotionally. He serves as an adviser to Shane, then to Rick. Dale also has a close bond with Andrea and Amy.
Steven Yeun as Glenn Rhee, a former pizza delivery boy, who knows his way around Atlanta and often embarks on dangerous supply runs for the group. Glenn is a highly intelligent and resourceful, though slightly cocky yet hopeful individual, who cares for everyone yet he is easily taken advantage of by the other group members; Rick trusts him on supply runs.
Chandler Riggs as Carl Grimes, Rick and Lori's son. He and his mother are taken to Atlanta by Shane after the initial outbreak.

tag: ul

text: Supporting cast[edit]

text:
Emma Bell as Amy, Andrea's younger, childish and innocent sister; both have a close bond with Dale. Amy is shown to generally care for the children in the camp.
Norman Reedus as Daryl Dixon, Merle's equally aggressive and volatile younger brother and hunter.[15] Unlike Merle, however, Daryl is far more reasonable and willing to follow the group's lead.
IronE Singleton as Theodore "T-Dog" Douglas, a fellow survivor in the Atlanta group. T-Dog is a man of honor and duty, who always tries to do what's right by people even if they don't deserve it or he doesn't like it, and is heavily burdened when he makes mistakes and always tries to make it right.
Melissa McBride as Carol Peletier, Lori's best friend since the outbreak occurred and the mother of Sophia and the friendly yet soft-spoken wife of Ed.[16]
Jeryl Prescott Sales as Jacqui, a member of the group, who is the only survivor of her family and a former zoning office worker.
Andrew Rothenberg as Jim, a mechanic and a quiet yet tortured member of the group, who saw his wife and children killed and eaten by walkers.
Juan Pareja as Morales, another member of the group, who knows the city's infrastructure and puts his family first, and is also a fairly optimistic person.
Madison Lintz as Sophia Peletier, Carol and Ed's quiet daughter, and Carl's best friend.[17]
Adam Minarovich as Ed Peletier, Carol's abusive husband and Sophia's father.[18] He frequently has issues with Shane and is implicated to have also abused other women at the camp.
Maddie Lomax as Eliza Morales, daughter of the aforementioned Morales and Miranda. She is the older sister of Louis.[19]
Viviana Chavez-Vega as Miranda Morales, wife of the aforementioned Morales and mother to Eliza and Louis.[20]
Noah Lomax as Louis Morales, son of the aforementioned Morales and Miranda. He is the younger brother of Eliza.[21]
Noah Emmerich as Dr. Edwin Jenner, a pathologist in the Atlanta CDC looking for any kind of cure.[22]

text: Guest cast[edit]

text:
Lennie James as Morgan Jones, Duane's father, Jenny's husband and the first survivor that Rick encounters.[23][24]
Michael Rooker as Merle Dixon, former military and drug dealer and Daryl's racist, volatile and unreasonable older brother, who is also a hunter. His volatile tendencies often put him at odds with the group.
Jim R. Coleman as Lambert Kendal, a police officer, who works with both Rick and Shane.[25]
Linds Edwards as Leon Basset, a somewhat inexperienced police officer, who works with both Rick and Shane.[26][27]
Keisha Tillis as Jenny Jones, Morgan's wife and Duane's mother.[28]
Adrian Kali Turner as Duane Jones, Morgan and Jenny's son.[29][30]
Noel G. as Felipe, a member of Guillermo's gang, the cousin of Miguel and the grandson of "Abuela".[31]
Neil Brown Jr. as Guillermo, the leader of a Vatos group in Atlanta taking care of a hospital.[32]
Anthony Guajardo as Miguel, a teenage member of Guillermo's gang, Felipe's cousin and "Abuela's" grandson.[33]
Gina Morelli as "Abuela", Felipe and Miguel's grandmother.[34]
James Gonzaba as Jorge, a member of Guillermo's gang.[35]

text: The series features several actors Walking Dead developer Frank Darabont has worked with previously, including Laurie Holden,[36] Jeffrey DeMunn, Melissa McBride and Juan Pareja. All four appeared in his 2007 film The Mist, along Samuel Witwer,[37][38] who appeared as a dying soldier,[39] and with Thomas Jane, who originally was set to star in the series when it was pitched to HBO.[40] It was wanted to be Rick Grimes.[41] He is also in talks with Darabont to possibly guest star on the series.[42] Laurie Holden also appeared in the 2001 film The Majestic (she played Adele Stanton, Jim Carrey's love interest), which Darabont directed. DeMunn has additionally appeared in several of Darabont's films, in addition to The Mist and The Majestic: The Shawshank Redemption (1994) and The Green Mile (1999).

text: Promotion[edit]

text: The show's official website released a motion comic based on the first issue of the original comic and voiced by Phil LaMarr.[43] The site also posted a making-of documentary primarily about the first episode, as well as a number of other behind-the-scenes videos and interviews. In the documentary, comic series creator and show executive producer Robert Kirkman as well as artist Charlie Adlard expressed that they were pleased with how faithful the show is to the comic and remark on the similarities between the actors and the comic's original character drawings.[44] Several scenes from "Days Gone Bye" were screened July 23, 2010 as part of the 2010 San Diego Comic-Con International.[45] Hurd asserted that "[they] really are doing six one-hour movie",[46] and Darabont insisted that the series would closely reflect the development in the comics. "The path is a very strong template. But we're going to take every interesting detour we feel like taking. As long as were staying on the path of what Robert has done, I don't see any reason not to. If they have patience we'll eventually catch up to what Robert is doing."[46]

text: The Walking Dead debuted during the same week in 120 countries. "Days Gone Bye" premiered in Hong Kong on TVB Pearl on August 30, 2011,[47] while it expanded in international markets during the first week of November.[48] Two weeks prior to its official premiere in the United States, the contents of the episode leaked online.[49] As part of an expansive campaign to advertise and heighten anticipation for the premiere, international broadcasting affiliates of AMC and Fox coordinated a worldwide zombie invasion event proceeding days prior to premiere of the episode in the United States. The event occurred in twenty six cities worldwide,[50] and were hosted in select locations including the Brooklyn Bridge in New York City, Lincoln Memorial in Washington, D.C., Palace of Westminster in London, Bosphorus Bridge in Istanbul, Acropolis of Athens in Athens, and the Museo del Prado in Madrid.[50][51] The campaign events commenced in Hong Kong and Taipei, and culminated in Los Angeles.[51]

text: The Walking Dead was included on the cover of the December 2010 edition of Entertainment Weekly, which featured Rick Grimes pointing a gun at a horde of walkers.[52] According to the journalist of the magazine, it "examines the past, present, and future" of the television franchise; "from the comic book's humble beginnings, to unlikely path to the small screen, to even more unlikely path as a bona fide hit."[52] Kirkman was ecstatic upon hearing of the news. "I've got to say—not to kiss your magazine's a– or anything—but when they called me and said Frank [Darabont] wanted to do the show, I was like, 'Yeah, I'll believe it when I see it.' And then when AMC was like, 'We're picking up the show,' I was like, 'Yeah, alright, whatever.' When they actually started shooting the pilot I was like, 'Well, this is kind of real, this is neat.' But when they called me and said, 'Your show's on the cover of Entertainment Weekly,' I think that was the first time I was like, 'Oh my god, I can't believe this is happening to me!'"[53]

text: Episodes[edit]

text:
No.overallNo. inseasonTitleDirected byWritten byOriginal air dateU.S. viewers(millions)11"Days Gone Bye"Frank DarabontTeleplay by : Frank DarabontOctober 31, 2010 (2010-10-31)5.35[54]
Sheriff's deputy Rick Grimes wakes from a gunshot-inflicted coma to discover the world overrun with walkers. He goes back to his house to find his wife and son but meets survivor Morgan Jones and his son Duane. Rick decides to head to Atlanta to find his wife Lori and son Carl, unaware they are safe with other survivors led by his former partner Shane). He encounters hordes of walkers and becomes trapped inside a tank.
22"Guts"Michelle MacLarenFrank DarabontNovember 7, 2010 (2010-11-07)4.71[55]
Rick is ambushed by a walker horde but is rescued by scavenger survivor Glenn when he becomes trapped inside a tank. They meet up with the rest of the survivors where they have to leave Merle handcuffed to the roof to stop him attracting walkers. They are forced to leave Rick's gun bag behind as well as abandon the unhinged Merle as walkers surround them, but manage to escape the city.
33"Tell It to the Frogs"Gwyneth Horder-PaytonStory by : Charles H. Eglee & Jack LoGiudice Teleplay by : Charles H. Eglee & Jack LoGiudice and Frank DarabontNovember 14, 2010 (2010-11-14)5.07[56]
Glenn takes Rick to the survivors' camp, where he finds Lori, Carl, and Shane. Rick leads a group, including Glenn, T-Dog, and Merle's younger brother, Daryl back to Atlanta to recover his weapons, finding that Merle managed to free himself by sawing off his hand.
44"Vatos"Johan RenckRobert KirkmanNovember 21, 2010 (2010-11-21)4.75[57]
Rick's group briefly scuffles with a group of Latino survivors protecting the residents of a nursing home in Atlanta, who want Rick's weapons, but Rick is able to defuse the situation peacefully. They return to camp too late to stop a walker horde from attacking, killing Andrea's sister Amy, and Carol's husband Ed.
55"Wildfire"Ernest DickersonGlen MazzaraNovember 28, 2010 (2010-11-28)5.56[58]
As the survivors bury their dead, some split off on their own. Rick, against Shane's judgement, leads the rest to the CDC facility in Atlanta, which initially appears abandoned and locked-down, but Rick spots signs of life and demands entry.
66"TS-19"Guy FerlandAdam Fierro and Frank DarabontDecember 5, 2010 (2010-12-05)5.97[59]
Dr. Edwin Jenner of the CDC welcomes the survivors, allowing them to enjoy the amenities of the powered building while explaining what he knows about walkers. When the survivors discover that the building will self-detonate once it runs out of backup power, Dr. Jenner initially prevents them from leaving. Rick convinces Jenner to let them go, and Jenner whispers something to Rick. They escape just before the building explodes, and the group departs the city.

text: Reception[edit]

text: Critical response[edit]

text: The first season of The Walking Dead received mostly positive reviews from critics. On Metacritic, the season holds a score of 82 out of 100, indicating "universal acclaim", based on 25 critics.[60] On Rotten Tomatoes, the season holds an 89% with an average rating of 7.49 out of 10, based on 24 reviews, and an average episode score of 87%. The site's critical consensus reads: "Blood-spattered, emotionally resonant, and white-knuckle intense, The Walking Dead puts an intelligent spin on the overcrowded zombie subgenre."[61] Following the pilot episode's debut, TV Guide's Matt Roush called the show "a stark and harrowing survival parable ... visually stunning ... and daring in its artful use of silence."[62] Following the second episode, Simon Abrams from Slant Magazine awarded the show three and a half stars out of a possible four; "To say that Darabont has kicked his series off with a bang would be a serious understatement ... [he] has fashioned a fully realized alternate reality and it's a thrilling thing to experience."[63]

text: In response to the season finale, James Poniewozik of TIME magazine gave the first season of The Walking Dead a glowing review stating, "the show has an urgency and bravery that make it something special".[64] Josh Jackson of Paste magazine also praised the season by writing, "the characters are worth caring about" despite "occasional stilted monologues, quick tempers and unfortunate stereotypes".[65] Some reviews were mixed, including one from Kofi Outlaw of Screen Rant who concluded, "The Walking Dead still hasn't really defined itself as anything more than a vague survival story about the human condition" but added, "you can be sure I'm one of those Dead-heads already chomping at the bit for season 2".[66] Sean McKenna of TV Fanatic also offered mixed criticism saying the first season "had its ups and downs" noting that the second season should focus on "a more specific story arc and strengthening of the character development".[67] Logan Hill of New York magazine was more critical, claiming the episodes contained "atrocious dialogue" and "a lot of plot machinery that has been contrived to create action suspense but ... hasn't really moved the story itself anywhere in particular", though he admits the fifth episode showed "flashes of promise".[68]

text:
The Walking Dead (season 1): Critical reception by episode

Season 1 (2010): Percentage of positive reviews tracked by the website Rotten Tomatoes[61]

text: Accolades[edit]

text: The first season of The Walking Dead was named one of the Top 10 Television Programs in 2010 by the American Film Institute.[69] The season was also nominated for Outstanding New Program at the 27th TCA Awards[70] and Best New Series at the 63rd Writers Guild of America Awards.[71] It was also nominated for Best Television Series – Drama at the 68th Golden Globe Awards[2] and Best Drama Series at the 1st Critics' Choice Television Awards.[72] For the 37th Saturn Awards, the season received six nominations, winning Best Television Presentation.[73] The nominations were for Best Actor on Television (Andrew Lincoln), Best Actress on Television (Sarah Wayne Callies), Best Supporting Actor on Television (Steven Yeun), Best Supporting Actress on Television (Laurie Holden), and Best Guest Starring Role on Television (Noah Emmerich).[74]

text: The pilot episode, "Days Gone Bye", received three Primetime Emmy Award nominations for the 63rd Primetime Creative Arts Emmy Awards, winning Outstanding Prosthetic Makeup for a Series, Miniseries, Movie, or Special, and received nominations for Outstanding Sound Editing for a Series and Outstanding Special Visual Effects.[3] Frank Darabont was nominated for Outstanding Directorial Achievement in Dramatic Series for his work on "Days Gone Bye".[75]

text: Ratings[edit]

text: The pilot received 5.3 million viewers, making it the most-watched series premiere episode of any AMC television series.[76] The first-season finale received 6 million viewers, a season high; with 4 million viewers in the 18-49 demographic, making it the most watched basic cable series for the demographic.[77] The first season had an average of 5.24 million viewers and a rating of 2.7 in the 18-49 demographic.[78] In the United Kingdom, it premiered one week after it did in the United States, on November 5, 2010 on digital channel, FX. The premiere had 579,000 viewers, almost double for any other show on FX that week. The viewership dipped during the season then rose to 522,000 viewers for the final episode.[79] The terrestrial premiere on Channel 5 on April 10, 2011, averaged 1.46 million viewers.[80] Based on its ratings, the series was renewed for a second season on November 8, 2010.[5]

text:
No.

Title

Air date
Rating/share(18–49)
Viewers(millions)

1

"Days Gone Bye"

October 31, 2010
2.7/7
5.35[54]

2

"Guts"

November 7, 2010
2.5/7
4.71[55]

3

"Tell It to the Frogs"

November 14, 2010
2.5/7
5.07[56]

4

"Vatos"

November 21, 2010
2.4/6
4.75[57]

5

"Wildfire"

November 28, 2010
2.8/7
5.56[58]

6

"TS-19"

December 5, 2010
3.0/8
5.97[59]

text: Home media releases[edit]

text: The first season was released on DVD and Blu-ray in region 1 on March 8, 2011[81] and in region 2 on May 16, 2011.[82] Special features on the sets include six featurettes—"The Making of The Walking Dead", "Inside The Walking Dead: Episode 1–6", "A Sneak Peek with Robert Kirkman", "Behind the Scenes Zombie Make-Up Tips", "Convention Panel with Producers" and "The Walking Dead Trailer". Also included are other behind the scenes featurettes—"Zombie School", "Bicycle Girl", "On Set with Robert Kirkman", "Hanging with Steven Yeun", "Inside Dale's RV" and "On Set with Andrew Lincoln".

text: A three-disc special edition of the first season was released on DVD and Blu-ray on October 4, 2011. The sets include all the previous special features, plus brand new extras. The new extras include audio commentary on all six episodes, the black and white version of the pilot, and six new featurettes—"We Are The Walking Dead", "Bring Out the Dead: KNB and the Art of Making Zombies", "Digital Decay: The VFX of The Walking Dead", "No More Room in Hell: The Walking Dead Phenomenon", "Adapting the Dead" and "Killer Conversations: Frank Darabont & Greg Nicotero". In addition to the DVD and Blu-ray release, a limited edition Blu-ray collector's tin contains an exclusive wearable zombie mask from the National Entertainment Collectibles Association designed by the series own make-up artist, Greg Nicotero.[83]